#include <iostream>
#include <random>
#include <iomanip>
#include <atomic>
#include <sstream>

std::string uuid()
{
    std::random_device rd;
    std::mt19937_64 gernator(rd());
    std::uniform_int_distribution<int> distribution(0, 255);
    std::stringstream ss;

    for (int i = 0; i < 8; i++)
    {
        ss << std::setw(2) << std::setfill('0') << std::hex << distribution(gernator);
        if(i == 3 || i == 5 || i == 7)
        ss << "-";
    }

    static std::atomic<int> seq(1);
    size_t num = seq.fetch_add(1);
    for(int i = 7;i >= 0;i--){ 
        ss << std::setw(2) << std::setfill('0') << std::hex << ((num >> i * 8) & 0xff);
        if(i == 6 ) ss << "-";
    }

    return ss.str();
}

int main()
{

    std::cout << uuid() << std::endl;
    return 0;
}